Experimental Study on the Influence of Hypergravity on the Nonlinear Flow Behaviour in Rock Fracture

Understanding the effect of hypergravity on the flow behavior in fractures is essential for using centrifuge modeling to study fluid flow and solute transport in fractured rock. Normal gravity (1 g) and hypergravity (N g) fracture flow experiments were carried out. The hypergravity effect on fracture flow was analyzed. The transition from linear to nonlinear flow was analyzed using the nonlinearity factor and the critical Reynolds number (Re-cr). The results showed that when the Reynolds number Re > Re-cr (162), the relationship between the total hydraulic gradient and the flow rate exhibited nonlinear flow behavior both in the 1 g and different N g experiments. The fitting curves of the total hydraulic gradient and the flow rate were similar, indicating that hypergravity had a negligible effect on fracture flow. Compared to the theoretical results that deduced from the Cubic law, the experimental results of 20, 25, and 30 g hypergravity experiments showed that the difference in the flow velocity was 0.08-2.93% when Re <= Re-cr (162), verifying that the similarity ratios of the flow velocity and fracture aperture were N: 1 and 1: 1 (model: prototype), respectively. These results are valuable for carrying out hypergravity experiments to predict the flow and migration of solutes/contaminants in large-scale fractured rocks, such as the long-term barrier performance of deep geological repositories.